Ok all sorted. Drill the holes and get them sealed. The two inside tanks are balanced. Then when I use the manifold and turn that on all 4 tanks are balanced and drain evenly. Thus one level sigbt. On that what am looking for as far fittings for it. I have two large brass ( outlets for the two standard tanks and three small brass fittings. My thinking is two for the sight level and only one return to one tank seeing they are balanced. ??
I have the on off Tao and fittings. Two breathers. Two outlets and then three small fittings. Return and sight level ???
Lyndon